Traditionally, the support structure between the wing flight controls and the spar/skin overhang on a large passenger aircraft consists of metallic ‘A-frame’ hinge ribs. These hinge ribs are traditionally formed from an aluminum alloy, attached to upper panels which overhang the rear spar of the wing, and their leading edge is in abutment with the rear spar. Interface loads from the flight control surface and air pressure loads are reacted by the hinge ribs into the rear spar of the wing and into the upper panels The upper panels are normally made of composite materials and they provide stability to the hinge ribs.
Alternative hinge rib designs such as shear webs can offer a more weight-optimized structural solution but may be less efficient in material cost and are worse for systems installation. Also shear webs can also cause significant thermal problems as they will tend to act as baffles to any global airflow that would normally aid the cooling process along the trailing edge of the wing.
Using the traditional single-piece ‘A’ frame does not make optimum use of the material or billet from which the hinge rib is machined, resulting in a large amount of waste. Also the grain flow in the billet can never be fully structurally optimized in the ‘A’ frame as the longitudinal grain flow of the material can never be aligned to both the legs of the ‘A’ frame, which may be at angles of up to 90 degrees to each other.